Ethernet Cable Jacket Ratings: CM, CMR, and CMP

Since Ethernet cables are often installed inside walls and ceilings, they must comply with fire safety standards. The National Electrical Code (NEC) establishes fire resistance ratings for Ethernet cables, with the most common being CM, CMR, and CMP. The following sections provide a detailed analysis of the CM, CMR, and CMP Ethernet cable jacket fire ratings to help you understand and select the appropriate fire-resistant cable.

CM, CMR, and CMP Cable Jackets: What Are They?

CM Cable Jacket

CM stands for "Communications Multipurpose." It is a cable jacket fire rating defined in NEC Article 800. The CM cable jacket fire rating is the most basic Ethernet jacket fire rating specified by the UL 1581 and CSA FT1 industry flame test standards.

CM-rated Ethernet cables are made from relatively low-cost Polyvinyl Chloride (PVC). Their jacket rating typically meets the minimum requirements for in-wall installation of Ethernet cables and is suitable for internal installation in residential or single-story commercial buildings. Like all in-wall rated Ethernet cables, the goal is to prevent fire from spreading along the cable from one part of a building to another. Ethernet cables marked "CM" must pass standardized flame resistance tests before they can be put into use.

CMR Cable Jacket

CMR stands for "Communications Multipurpose Cable, Riser." It is a cable jacket fire rating defined in NEC Article 800. The CMR cable jacket fire rating is a flame-resistant jacket standard specified by the UL 1666 and CSA FT4 standards.

So, what is a CMR cable? CMR cables are made from relatively inexpensive Polyvinyl Chloride (PVC) and insulated with high-density Polyethylene (PE). Also known as "Riser-rated cable," they are commonly used in vertical cabling applications. They are designed to prevent fire from spreading between floors through risers or shafts. The fire resistance requirements for CMR cables are much stricter than those for CM cables. CMR cables have better flame-retardant properties and are therefore more expensive.

CMP Cable Jacket

CMP stands for "Communications Multipurpose Cable, Plenum." It is a cable jacket fire rating defined in NEC Article 800. CMP is the highest grade of Ethernet jacket fire rating, complying with the UL 910 Plenum test and CSA FT6 standards.

CMP cables feature a Fluorinated Ethylene Polymer (FEP) insulation and a low-smoke Polyvinyl Chloride (PVC) outer jacket. Also known as "Plenum-rated cable," they are suitable for installation in plenum spaces like air handling ducts, drop ceilings, or raised floors. CMP cables (Plenum-rated cables) limit flame propagation to within five feet and reduce the amount of smoke generated during a fire. Due to the use of cleaner, more self-extinguishing materials, they do not release toxic gases when burned.

CM, CMR, and CMP: What's the Difference?

Now that you understand the various Ethernet cable jacket types and their fire ratings, let's summarize the differences between CM cable, Riser-rated cable, and Plenum-rated cable in the table below.

Given these differences, how do you choose the right fire-resistant cable?

CM, CMR, and CMP: How to Choose?

To maximize cabling performance, it is essential to ensure that the selected fire-resistant cable type meets the standards required for your specific project.

CM Cable: Used for direct connections between equipment over short distances. You can choose the CM option if you are using the cable on the same floor, or in residential and commercial buildings.

CMR Cable: If you do not need to run cables through air handling plenums, CMR cable is also a good choice. It is more cost-effective than CMP cable and offers a relatively high safety standard.

CMP Cable: CMP cable meets various cable needs. CMP cables comply with the most stringent safety standards, reducing the risk of inhaling toxic fumes in the event of a building fire, providing peace of mind.

Now that you know about CM, Riser-rated, and Plenum-rated cables, make an informed choice based on your needs.

Related Terms: CMX, PVC, and LSZH

CMX: CMX is another type of cable jacket. CMX jacketed cables, made from Linear Low-Density Polyethylene (LLDPE), are UV and weather resistant. They can withstand intense sunlight, strong winds, rain, and extreme temperature changes. However, they do not have a fire rating.

PVC: As mentioned above, PVC is the material that makes up the Ethernet cable jacket, with protection ratings of CM, CMR, and CMP. Ethernet cables marked PVC CM, PVC CMR, or PVC CMP are often seen on the market.

Low Smoke Zero Halogen (LSZH) cables are made with jacket materials free of halogens and are suitable for various applications. LSZH cables perform slightly worse than Plenum-rated cables and are primarily sold in Europe.

Fibermart Cable: Bulk Ethernet Cables, Offering CM/CMR/CMP Options

Fibermart offers a variety of bulk Ethernet cables, covering Cat5e, Cat6, Cat6a, and Cat7 types. With CM, CMR, and CMP cable jacket ratings, we meet your different deployment needs. Fibermart bulk cables use innovative processes to ensure performance and safety, featuring user-friendly designs for an optimal experience. Fibermart Bulk Ethernet Cables are ideal for various network applications such as offices, hotels, smart homes, and data centers. Furthermore, Outdoor Direct Burial Cables provide another option for extending your internet connection, offering stable operation even in harsh or extreme environments, making them perfect for your outdoor or underground installation projects. Find the right cable for your project at Fibermart.